Electrical positioning system



Oct. 2z, 194e. G. H. PHELPS 2,409,895

ELECTRICAL POSITIONING SYSTEM F-l'ed Feb. 5, 1943 2 Sheets-Sheet 1 figliWITNESSES: INVENTOR @4W f i @wege/Ww@ BY 74. I I SR YQ Oct. 22, 1946. G,H PH'ELPS 2,409,895

ELECTRICAL PQSITIONING SYSTEM Filed Feb. 5, 1945 2 sheets-sheet 2ATTORNEY Patented Oct. 22, 1946 UNITEDy vSTATES PATENT OFFICE tELECTRICAL POSITIONING SYSTEM George H. Phelps, Catonsville, Md.,assignor to Westinghouse Electric Corporation, East VPittsburgh, Pa., acorporation of Pennsylvania Application February 5, 1943, Serial No.474,829

6 Claims. (Cl. 172-239) This invention relates to electrical positioningsystems and, more particularly, to a selective control of circuitelements from a remote point.

Positioning systems of the type to which this invention particularlyrelates include a motor drive rotatable in both directions which iscoupled to the driven element in such manner that the movement of thelatter can be set to various predetermined positions. In these systems,it is essential that the driven element should be accurately positionedalong a circular path to any preselected position, by rotation vineither clockwise or counterclockwise direction. Control systemsheretofore used generally employ a. split disc in cooperation with thedriving motor which rotates simultaneously with the i driven element.There is also a suitable electricalor mechanical clutch mechanism todisengage the motor when the driven element reaches theselectedposition. On the split disc are placed a number of contacts, eachdefining one selectedA position ofthe driven element. The insulatingspace which separates the two halves forms the dividing line between theltwo directions of rotation of the motor. The free space between the twosegments cooperates with the contacts so that when any one of thecontacts through which a circuit is completed to the `motor reaches thisspace it will open the circuit. f

When a split disc is used the rotation in each direction is confined to180. If rotation 4beyond' that is desired up to nearly 360 each half ofthe split disc may be replaced by individual contact discs carryingcontact segments which make .a complete revolution for each direction ofrotation.

While this type of remote control has been widely used, it has thedisadvantage that for very accurate positioning avery accurate and smallclearance must exist between the two halves .of thesplit disc segments.The slightest momentum of the turningdisc augmented by the momentum ofthe motor may cause overriding, whereby upon contact with the othersegment a reversal of the motor is effected. This conditioncreateshunting or oscillating around the desired point. Moreover, the accuracyofvpositioning is limited by the Width of the insulating space betweenthe discs which in practice has to be .wide enough to prevent hunting,and thereby allows appreciable differences in the actual stoppingposition.

'Ihe present invention overcomes these disadvantages when such systemsare used for the positioning of switches or other circuit components,

e 2 wherein each position represents equal angular displacements overthe path described by the arc of rotation. This is accomplished by theaddition of a cam switch driven by the motor which permits furtherrotation of the motor after the desired positioning has ybeenestablished.

Another advantage of the'positioning system herein described is that theusual clutch between the motor and the driven element can be eliminatedby utilizing a novel drive inthe form of a Maltese-cross gear, so thatthe accuracyY of the setting is determined thereby.

A particular feature of the invention resides in an extremely compact vmechanical assembly whichI is easily adapted to effect the positioningof any number of selector switches accurately to any preselected stop. Y

Another feature of the invention, as will be seen when considering itsmechanical details, re-

sides in the drive mechanism for the vMaltesecross gear which maintainsa rigid contact position for the selector switches driven thereby.

A marked advantage ofthe system herein described is its freedomfromtemperature variationsin that prior tor the movement of the actuatedelement no actuating motor may start under no-load condition and may runfor a definite time freely. In this manner operation is secured whentemperature conditions adversely affect the motor speedandpower. v

. Other features and advantages will be apparent from the followingdescription of the invention, pointed out in particularity by theappended claims, and taken in connection with the accompanying drawings,in which:

Figs.A 1, 2-and 3 show three views of the compact driving mechanism-as aunit which can be attached to any desired number of selector switches;Fig. 4 shows` a .schematic circuit arrangementv for thefcontrol of thepositioning mechanism in combination, by way of example, with the tuningmechanism of a radio receiver to-a number of preselected frequencies.

Referring to the drawings, in the viewsof Figs. 1, 2 and 3, the drivingmotor I is shown to be mounted in a frame 2the motor having a shaft 3carrying a worm 4. The latter drives the worm gear 5, the shaft 6 ofwhich runs transverse to the frame 2 in bearings I and 8. Secured to theshaft 6 and driven thereby is the lock wheel 9 carrying the pin I 0 .fordriving the Maltesecross wheel I2. On the other'y side of the gear 5,the shaft 6 carries the cam I3, the surfaceY of which engages themovable member I4 of the holdlover switch I 5. 'I'he Maltese-cross wheelI2 drives the shaft I1 at one end, and at the other end it rotates thecircuit control switch I8 and the connecting switch 20 for the hold-overswitch I5. The shaft I1 protrudes sufficiently to permit couplingthereto the selector switches which the device is intended to position.In other words, to the shaft I1 is connected the driven element of thepositioning system.

The mechanical features should be observed in these figures for aclearer understanding of the system when considering the operationthereof in connection with the various electrical controls. It is seen,taking particularly Figs. 2 and 3 into consideration, that as the motorshaft 3 revolves the lock wheel 9 is turned by the worm gear 5.

The lock wheel 9 carries the locking member II which engages thecorresponding peripheral face of segment IB, of the Maltese-cross wheelI2.. As long as the member II engages the surface of the segment I6, theMaltese-cross wheel I?. is locked in position. At every revolution oithe lock wheel 9, the pin I engages the slot I9 between the segments IBand will drive the wheel I2 one segment in either direction dependingupon the direction of rotation oi the wheel 9. When the pin Hl engagesthe slot I9, the cutout portion of the member II unlocks the wheel I2,permitting movement thereof. It is to be noted that once the pin I0leaves the slot I9, the wheel 9 is free to rotate Without affecting thefirm position of the Maltese-cross I2. In this manner, as will beexplained later, the -motor may continue its rotation over acomparatively long segment in the circular -path of the pin I0, and maybe stopped anywhere along this segment without interfering with thesucceeding positioning of the Maltese-cross I2. This is an importantfeature and instrumental in the absolute accuracy of each step in thepositioning of the shaft I1.

Referring now to the operation of the system and observing the circuitshown in Fig. A4, it is seen that the important mechanical elements areshown in vperspective and the electrical circuit is schematicallyrepresented. For the purpose of clear illustration, the control switchesand the various mechanical elements are spaced far apart, andparticularly the shaft I1 is shown extended. Coupled to the shaft isshown, by way of example, a set of rotary switches for the remoteactuation of the tuning of a radio receiver. The electrical positioningdevice in accordance with this invention is well adapted for use inconnection with radio receivers, and for this reason it was chosen toillustrate its operation in connection with a radio receiving system. Itis to be understood and can readily be seen that, in place of the tuningarrangement of the radio receiver, other types of rotary switches may beactuated for a variety of purposes, such as selecting differentelectrical circuits. While there are only two switches shown, any numbermay be employed as long as they are to be actuated simultaneously. Theswitches may also have any number of contacts provided that theMaltese-cross wheel segments are accordingly proportioned and the sizeof the circuit control switch I8 allows the placement of the number ofriding contacts desired side-by-side along the two operating segments 22and 22 respectively. To avoid unnecessary complication of the circuit,there are only three contacts shown, sufficient it is believed for a`thorough understanding of the operation of the system.

The terminals A and B indicate the connection to a source of power fordriving the motor I. This source may be either alternating or directcurrent. The motor is of the dual* iield type, having iields 23 and 24.One terminal of each iield connects to one side of the incoming supplyline in series with the armature or rotor which contacts brushes 25 and2E. The other terminal of field 23 connects through lead 21 to the rider28 of the circuit control switch I8 engaging the segment 22, and alsothrough lead 29 to the upper contact of the hold-over switch I5.Similarly, the other terminal of field 24 .connects through lead 30 tothe rider 3| which engages segment 22' of the circuit control switch I8,and also to the lower contact of the hold-over switch I5. Displacedaround the switch I9 are the contacts 32, 33 and 3d, equidistantlyplaced corresponding to the number of steps which the positioning systemis to make in its intended operation. Connected in parallel with theabovementioned contacts are the contacts 35, 36 and 31 of the connectingswitch 29, the rider of which is connected through lead 38 to the movingcontact I4 of .the hold-over switch I5. The contacts 39, 40 and 4I ofthe manual selector switch 42 connect also to contacts 32, 33 and 34,respectively. The manual selector switch 42 may be placed at any desiredlocation and completes the current path to the source in that its rider43 is connected to the terminal B of the supply.

The radio receiver shown here comprises a simple ampliiier and detectorcircuit tunable by means of the iiXed condensers 41, 48 and 49 in theampli-lier stage and the fixed condensers 50, 5I and 52 in the detectorstage. Each of these condensers is indicated to be variable for aparticular setting to tune the receiver to a desired station. Selectorswitch 53 connects any one of the condensers 41, 48 or 49 to the grid`55 of the Vacuum tube `56, tuning thereby the grid circuit comprisingthe secondary 51 oi the radio frequency input transformer 58. Similarly,the selector switch 54 connects any one of the condensers 5I), `5I or 52in shunt with the secondary 59 of the coupling transformer 60. Thevarious circuit elements of the radio receiver have no bearing on theinvention herein described and need not be considered in detail. Sufficeit to say that when switches 53 and 54 connect corresponding contacts,the radio receiver is tuned to receive a selected station.

Describing the operation, let us assume that the entire system is atrest. It is seen that following the circuit from the A terminal, themotor iields 23 or 24 are not energized, since the connection to thefield is broken in that neither switch I8 nor switch I5 is closed to thecontacts selected by switch 42. Thus the center contact 40 of the switch42 was chosen as the desired position when the system was last operated.Following the connection to the center contact 33 of the switch I8, Wesee that the circuit is broken by the insulation between the segments 22and 22. Furthermore cam I3 is in such position that the moving contactI4 of the switch I5 is between the upper and the lower contacts.

Let us now turn the manual selector switch 42 to the position wherebyits rider 43 engages the contact 4I. Following the circuit from the Bterminal, we see that the current will flow through the contact 34 ofthe switch I8 and finds a path along the segment 22 to the contact 3|and through lead 39 to the field 24 and through the motor to theterminal A. It should be noted also that the rider of the switch 2D doesnot engage the contact 31, so that the moving arm I4 of the switch I5,is not connected to the current source.4 The purpose of the switch 20will be better understood when the` operation ofthe system becomes clearand will be explained hereafter in greater detail'.

We have seen that the field 24 become'fene'rgized, when the switch 42was moved to energize contact 4I. The connections of the motor elds areso made that when the eld 24 is energized, the motor will turn the worm4 so as to rotate the worm-gear 5 in the proper direction whereby theMaltese-cross wheel I2 moves the shaft I1 so that the contact 34 of thecircuit control switch lI8 shall be placed between the segments 22 and22. In accordance with the operation in the manner chosen it is seenthat the rotation of the worm gear 5 must be counterclockwise asindicated by the arrow,` since movement of the drive pin I I) in thisdirection will rotate the Maltese-cross wheel I2 in a clockwisedirection. It should be noted here that as the worm gear 5 rotates andthe pin IIJ approaches the Maltese-cross wheel I2, the cam I3 will liftthe moving arm I4 of the switch I5 so that it engages the upper contactthereof. However, this in no way inuences the rotation of the motor I inthe direction indicated in that, as can be seen in tracing the circuit,the field 23 is not connected to the source, because the circuit throughcontact I4 and upper contact I5 is broken at contact arm 20 of theswitch 20 and also at contact 39 of the switch 42. As the drive pin I 0moves the Maltese-cross wheel I.2 one step and shaft I1 is turnedthereby, the switch I8 will be moved so that the segment 22 no longerengages the Contact 34. The latter` will be now in the same position as.the contact 33 was previously, that is, the circuit therethrough willbe broken. At

the same time, the switch 2D will engage con-A tact 31. rI'he switches53 and 54 are now also positioned so that condensers 41 and 50 areplaced across the respective circuits of ythe receiver. The instant whenthis occurs the drive pin IU will be just ready to leave the slot, andthe motor would stop since the contact 34 is not in engagement with thesegment 22', and the circuit is broken between contacts 34 and 3|.However, the operation' of the hold-over switch I3 assures continuedrotation of the motor and also, of course, of the pin Il) of the lockwheel 9. The reason for this is that the cam I3 will now oier thesmaller diameter of its contours to the moving arm I4 of the hold-overswitch I5, so that the lower Contact thereof is in engagement. Intracing the circuit, we see that the current starting from the terminalB will iiow through contact 4I of the switch 42, contact 31 of theswitch 20, through lead 38 and the lower contacts of the hold-overswitch I5 through the iield 24. The rotation will continue until the camI3 reaches the original starting position shown, whereby the arm I4 ofthe hold-over switch I5 is again in the mid-position between the upperand lower contacts. Whatever momentum the motor may have had, includingthe momentum of the worm gear '5 and lock wheel 9 which would tend tocontinue rotation of the motor even after the arm I4 of. the hold-overswitch I5 breaks the circuit, will not affect the accuracy of thesetting of the driven elements in that the Maltese-cross wheel stays inlocked position over a substantial travel of the drive pin I0. Thestopping surface 44 of the cam I3 has sufficient length to allow for themovement due to momentum when the arm I4 is lifted from 6 the lowercontact toi break the circuit to the motor.

Considering now the operation of the switch 2li, it will be seen thatitis intended to control theconnection'of the arm I4 of the hold-overswitch I5 to the supply circuit in such manner thatwhen the manualselector switch 42 is placed to any desired contact for the next ensuingoperation, connection `to the arm I4 of the hold- 4over switch I5 isbroken until the shaft I1 is moved tothe selected position. Then contactof the hold-over switch arm I4 is again established through the newsetting of the switch 20.

I claim as my invention: Y

1. In an electrical positioning system, switchingA means adapted to bepositioned in denite steps over a series of contacts, a motor fordriving said means, an energizing circuit for said motor including acurrent source and a circuit control switch in series therewith operatedin conjunction with the positioning of said means,

'said circuit control switch determining also the direction offrotationof said motor, a selector switch adapted to be placed at a remote pointfor selecting at will the positioning of said switching means to any oneof the number of said series of contacts, said selector switchcompleting the energizing circuit through said control switch to saidmotor and a hold-over switch maintaining said energizing circuit closeduntil the positioning of said switching means is fully completed andafter said control switch reaches its open circuit position.

2. In an electrical positioning system, switching means adapted to bepositioned in denite steps over a series of contacts, a motor fordriving said means, an energizing circuit for said motor including acurrent source and a circuit control switch in series therewith operatedin conjunction with the positioning of said means, said circuit controlswitch determining also the direction of rotation of said motor, aselector switch adapted to be placed at a remote point for selecting atwill the positioning of said switching means to any one of the number ofsaid series of contacts, said selector switch completing the energizingcircuit through said control switch to said motor and a hold-over switchoperated by a cam driven by said motor for maintaining said energizingcircuit closed until the positioning of said switching means is fullycompleted and after said control switch reaches its open circuitposition.

3. In an electrical positioning system, switching means adapted to berotatably positioned in definite angular steps over a series ofcontacts, a reversible motor for driving said means, an energizingcircuit for said motor including a current source and a circuit controlswitch in series therewith operated in conjunction with the rotation ofsaid means, said circuit control switch determining also the directionof rotation of said motor, a selector switch adapted to be placed at aremote point for selecting at will the positioning of said switchingmeans to engage any one of the number of said series of contacts, saidselector switch in series with said control switch completing theenergizing circuit to said motor, and a hold-over switch operated by acam driven by said motor for maintaining said energizing circuit closeduntil the rotation of said switching means is fully completed to theselected contact and after said control switch reaches its open circuitposition.

4. In an electrical positioning system, switching means adapted to berotatably positioned in denite equidistant steps over a series ofcontacts, va reversible motor for driving said means, an energizingcircuit `for said motor including a current source and a "circuitcontrol switch in series Vtherewith operated in conjunction lwith therotation of said means, said circuit control switch Ydetermining alsothe direction of rotation of said motor, a selector switch adapted to beplaced at a remote point for selecting at will the positioning of saidswitching means to any one of the number of said series of contacts,said selector switch completing the energizing circuit in series withsaid Icontrol switch to said motor and a hold-over switch `in `shuntwith said control switch for maintaining said energizing circuit closeduntil the positioning of said switch means is fully completed and aftersaid control switch reaches its open circuit position.

5. In an electrical positioning system, driving means comprising areversible motor, driven means, a drive between said motor and saiddriven means including `means for positioning said driven means to afixed step of `angular displacement for each complete revolution of saiddrive in either direction, an electrical control circuit for said motorincludinglmeans for determining the direction oi' rotation of saiddriven means and for selecting a particular step of displacement.thereof, and control `means for completing the revolution of said driveto substantially the same stopping point after said driven means vispositioned to a selected step.

6. In an electrical positioning system, driving means comprising areversible motor, driven means, `a drive between said motor and saiddriven means including a Maltese-cross coupling for positioning saiddriven means to a fixed step of 'angular displacement for each completerevolution of said drive in either direction, an electrical controlcircuit for said motor including switching means actuated by said drivenmeans for determining the direction of rotation of said driven means andfor selecting a particular step of displacement thereof, and controlmeans for said motor for completing the revolution of said drive tosubstantially the same stopping point after said driven means ispositioned to a selected step.

GEORGE H. PHELPS.

